His failure to give his full backing to Mr Balls will come as a blow to the Shadow Chancellor.

“I have the same rule for everybody across the Shadow Cabinet,” Mr Miliband said. “And it’s a very principled position, I am going to do nothing that’s about measuring the curtains.

“It’s the measuring-the-curtains thing. Why would you start naming your Cabinet two-and-a-half years before the election? Honestly.

“I think Ed Balls is doing a great job but I am not going to get into that.”

Mr Miliband said there is still no indication that his brother, the former foreign secretary, wants to return to the Shadow Cabinet.

“My position on David is absolutely consistent, my door has always been open and remains open for David to come back,” Mr Miliband said.

“He has made very clear that at the moment he’s not coming back into the Shadow Cabinet and he is doing other important work on the whole range of areas such as on youth unemployment and on the environment.”

The Labour leader added: “Look, of course it was a bruising leadership contest and as time goes on that sort of recedes and that’s good for our relationship.

“I wouldn’t take it as indication about a change in his view he’s not coming back to the Shadow Cabinet – but the door is open.”

David Miliband gave a speech in the Commons yesterday in which he criticised his former boss Gordon Brown for engaging in the “politics of dividing lines”.

In a rare speech denouncing the Coalition’s benefits bill he said George Osborne, the Chancellor, has fallen into the same trap as former prime minister Mr Brown did during the “dog days” of the Labour government.

He said the Coalition's current welfare bill "reeks of politics, the politics of dividing lines that the current Government spent so much time denouncing when they were in Opposition in the dog days of the Brown Administration".

He urged MPs to vote against the "rancid" legislation based on the claim that people on benefits are "choosing a Life of Riley".